Placebo Effect Exists with the Common Cold

Kate H. Gamble, Senior Editor

Published Online: Wednesday, July 13, 2011

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A study of 719 patients found that cold sufferers who get a pill, regardless of what it contains, have less severe symptoms and recover slightly earlier than patients who don’t take medicine. The placebo effect was most pronounced among people who believed in echinacea’s healing properties, according to the research, which is published in the July/August edition of the Annals of Family Medicine.

In the study, a cohort of patients aged 12 to 80 with new-onset common colds were divided into 4 groups. One group didn’t receive any treatment; another group of patients received echinacea and were told they were receiving the herb; and 2 other groups received pills but didn’t know the contents. The pills either contained echinacea or were a placebo.

Patients receiving pills were instructed to take 2 pills 4 times a day for the first 24 hours and then continue with 1 pill 4 times a day for 4 days. During the study, virus samples were obtained from participants’ noses. Patients were required to complete a survey twice a day to assess the severity of their illness, and were asked about their beliefs in echinacea as a potential cold treatment.

Overall, researchers didn't find major differences between the four groups, but the length and severity of colds was slightly worse among patients who didn't receive pills. Colds lasted about six to seven days in all groups.

There was little difference in the outcomes of those who didn’t know they were receiving echinacea and those who knew they were taking echinacea, which suggests that the herb didn't have a significant impact.

However, a subgroup of patients who rated echinacea’s effectiveness highly in a survey at the start of the study—and were given a placebo during the study—had the shortest duration colds. Their illnesses were 2.5 days shorter than those who weren’t taking pills.

The study also found 62% of patients who didn't receive pills reported headaches compared with less than 50% of patients in the other 3 treatment groups.
Researchers concluded that there can be a placebo effect with the common cold, particularly in people who believe in a therapy, but the effect is limited.

“These findings support the general idea that beliefs and feelings about treatments may be important and perhaps should be taken into consideration when making medical decisions,” they wrote.